It's hard to see this caterpillar when it is on a leaf

Camouflage of the Baron Caterpillar

This is a baron caterpillar. It is a cryptic bug, not a masquerading bug. From the Biological Journal of the Linnean Society:

Masquerade is also thought to differ from crypsis because cryptic individuals are mistaken for the background on which they rest, whereas masquerading individuals are mistaken for specific objects. As a result, crypsis relies on the relationship between the individual and the background, but the benefit of masquerade is thought to be independent of the background against which the masquerading individual is viewed…

Image of baron caterpillar on red surface: Vinayaraj/Wikipedia